What does the Migration Preparation Tool do?

During a recent issue with a SBS 2003 to 2008 migration, I was asked to explain what the Migration Preparation Tool does. Put on the spot, all I could remember as the AD Schema update and ...some other things.

So, here it is, verbatim from the MS Documentation:

The Migration Preparation Tool prepares the Source Server for the migration process by performing the following tasks:

Runs Adprep.exe, which extends the Active Directory Domain Services (AD DS) schema and updates permissions as necessary to prepare a forest and domain for a domain controller that runs Windows SBS 2008. The AD DS schema in Windows SBS 2008 is not the same as the schema for AD DS in Windows SBS 2003 or in Windows Server 2003. To successfully complete the migration process, you must update the AD DS schema on the Source Server if it is running Windows SBS 2003 or Windows Server 2003.

Important
It is recommended that you back up your Source Server before running the Migration Preparation Tool. All changes that the Migration Preparation Tool makes to the schema are irreversible. If you experience issues during migration, the only way to return the Source Server to the state before you ran the Migration Preparation Tool is to restore the system backup.


Installs an update that extends the time limit for finishing the migration process. Only one server running Windows SBS 2008 or Windows SBS 2003 is allowed to be a domain controller on your network. For a migration, you can have both domain controllers on your network for a limited time period. The update extends this time period to 21 days.


Prepares the server to migrate from Exchange Server 2003. For the migration process to be successful, Exchange Server must be in native mode, not in mixed mode. For more information about converting from mixed mode to native mode, see “How to convert from mixed mode to native mode in Exchange” at the Microsoft Web Site (http://go.microsoft.com/fwlink/?LinkId=104943).